It can’t be that in that case, but something down there did it. The evidence is totally clear.
Possible – but how probable you flew over it several times at the exact time the “something” was radiating?
Auvours is the base & training area of the 2nd Marine Infantry regiment, so not exactly big on RF.
There is high energy LF radio transmitter at Learmonth in Western Australia that has reportedly caused some autopilot upsets to overflying airliners…. One notable case was an A330 from Singapore to Perth in 2008….
https://www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-070.aspx
A few months later (27 Dec 2008) another QF A330 going the other way had an autopilot upset and disconnect at a similar range from the transmitter….. However no evidence has ever been found that RF interference was the cause….but the rumours persist…
The only way to prove this sort of thing is to fly the plane over the alleged problem location, with RF data logging equipment connected up to an antenna, and maybe also to various carefully chosen existing wires.
That is going to involve some effort and, in the case of an airliner especially, loads of money. What is the DOC of an A330, especially one which is in scheduled service? Must be well into 5 figures per hour.
“The aircraft that was involved in the 7 October 2008 occurrence was flown over
the station while it was transmitting. Measurements of the EMI environment on
the aircraft near the ADIRUs were undertaken, and no measurable influence
from the station was observed (Appendix F).”
Shorrick_Mk2 wrote:
“The aircraft that was involved in the 7 October 2008 occurrence was flown over
the station while it was transmitting. Measurements of the EMI environment on
the aircraft near the ADIRUs were undertaken, and no measurable influence
from the station was observed (Appendix F).”
Indeed…. As an aside the Qantas captain of that flight (actually an American) is a friend of one of my relatives and he told of his initial horror when the nose suddenly dropped of immediately pulling back on the game stick and the airplane did absolutely nothing….of course they sorted it out pretty quickly but that lack of immediate direct response from the “Airbus knows better” control system scared the crap out if him…
This is what an imminent servo burnout looks like
It works but there is an up/down motion. The video shows the yoke moving forward and back.
There is no apparent altitude change and no VS indication, but the pitch attitude is visibly varying, and one can definitely feel it.
In the past I have had a wire come off the tachometer in the pitch servo (detailed here on honeywell’s favourite website 
) which caused the gain of the servo to increase dramatically and made the pitch control loop unstable, but that caused a much bigger pitch oscillation.
I have a long flight home from Brac LDSB. It started doing this on the way down, and I am not carrying any spare servos this time. Obviously it cannot be fixed in the field (I have a copilot so will be fine) but I wonder if anyone has come across this rather low amplitude pitch oscillation.
It happens in the PIT mode too, not just in ALT hold, and happens during a climb (PIT or VS mode) or during a descent. Selecting alternate static (in case of water in the static pipes) does not stop it.
There is a very barely visible movement on the flight director – as one would expect.
Using the KFC 150 I had the same thing in the past. It startet with a small oscillation and became worse over the time. Finally there was a small spring broken in the servo. Easy to fix. Maybe your fault is similar.
I also have a KFC150 and have had this slight pumping for years. They haven’t found anything so far but it doesn’t necessarily point to an imminent failure.
Certainly this is not normal. Any AP which does this is unserviceable. I know some installations never worked properly but the KFC225 has always been rock solid (except for the failures as in the link above).
I will report on what is found.
